Showing papers on "Vehicle dynamics published in 1988"

On the optimal design of an automotive lateral controller

Abstract: An optimization approach is used to design a velocity-adaptive, lateral controller to meet requirements pertaining to lateral-position, tracking accuracy, robustness, and ride comfort. The resulting controller, which is nonlinear with velocity, requires full-state feedback and thus an observer is included. The observer/controller compensator was implemented using a 16-bit microcomputer and evaluated in a laboratory study wherein vehicle lateral dynamics were simulated on an analog computer. Excellent lateral control, i.e. close tracking (with absolute value of lateral-position error below 0.024 m in curve tracking), good sensitivity to disturbance forces, and probable ride comfort resulted. The selected control algorithm was realized using some 5% of the available computation time, thus allowing the microcomputer to be used for other control functions and vital-function monitoring. >

Integrated vehicle control

Abstract: The ever-increasing use of electronics and computers in our vehicles is apparent to everyone and many studies have clearly documented the dramatically increased electronic content in future vehicles. What's not so clear is how vehicle designers will take advantage of the increased possibilities represented by more electronics and computers to give the driver-vehicle system expanded capability and enhanced value to our customers. The essence of our work in Project Trilby is to create the concepts and bring together the technology for total, integrated control of our vehicles in order to provide our customers with a level of performance not otherwise achieveable. Total, integrated contro requires the coordination of all vehicle subsystems, while factoring the needs, performance and preferences of the driver into the design and control decisions. One possible scenario is an Adaptive Vehicle which would have: the capability for sensing or identifying its operational situation, an on-board knowledge or data base, the ability to analyze the situation relative to history and indicated driver preferences and performance capabilities, and then the ability to adapt the vehicle via control decisions to achieve the beat overall system performance. Worldwide, in the automotive industry and in other industries, there are similar efforts to capitalize on the continued maturing of computers and electronics, with the core question being the degree of intelligence and authority to be incorporated. The overall approach to design of such systems is dependent on: the use of analytical design techniques, including explicit representation of the driver, to understand configure the system; achieving coordinated control of the subsystems; and interfacing properly with the rapidly changing environment in which our vehicles must operate.

Analytical modeling of driver response in crash avoidance maneuvering. volume 1: technical background. final report

Abstract: The report describes a series of models and computer programs designed to analyze vehicle handling and driver/vehicle interaction in a variety of severe (collision avoidance) maneuvering scenarios. The volume provides technical background on the driver/vehicle/roadway system model, vehicle dynamics, maneuvering effects on vehicle handling, and driver/vehicle interaction. It discusses the importance of tire characteristics to vehicle dynamics and summarizes the development of a full-maneuvering tire model. It summarizes issues on vehicle load transfer to tires and its effect on tire characteristics and vehicle dynamics during maneuvering. It discusses linear analysis and nonlinear simulation of vehicle dynamics, driver models, driver/vehicle interaction, and summarizes crash avoidance scenarios using a driver/vehicle/roadway model. Computer programs to implement these models are discussed in other volumes in the series.

Dynamic terrain inputs to predict structural integrity of ground vehicles. Final report

Abstract: 1 6 Abafact This report presents a study and evaluation of the technology and methodologies available for predicting the response of mobile ground equipment to dynamic input from terrain roughness. The purpose of the report is to develop a technical foundation for the subsequent formulation of military specifications for durability of ground vehicles used at air bases. The report reviews the techniques and methods that have been used successfully to (1) model and analyze vehicle response to road roughness, (2) characterize pavemznt inputs to various vehicle models, (3) develop a standard roughness scale-the International Roughness Index (IRI), and (4) measure pavement profile, road roughness, and vehicle response. Specialized instruments are described for the measurement of road profile. The modeling of road inputs is further developed, based in part on extensive measured profile data. In particular, the correlation between the left-and right-hand wheeltrack profiles is modeled to match actual road data. The report concludes by relating technology and methods to the Air Force environment. A standard road representation is tentatively proposed, with several types of roughness that are most relevant for predicting vehicle response and possible failure. Considerations are given for measuring profile, adopting a roughness index, and validating vehicle analyses.

Development of Driver/Vehicle Steering Interaction Models for Dynamic Analysis

Abstract: : This document reports on the development of a computer-based model of driver steering control which can be used to represent and predict realistic steering responses of human operators during path-following and obstacle- avoidance maneuvers. The model is intended to be used for controlling different types of land vehicles over a range of operating conditions. The model was validated through direct comparison with experimental measurements of driver vehicle systems collected during this study. For conventional steering maneuvers, the model was shown capable of replicating most observed steering control behavior patterns through simple adjustment of two basic parameters. Driver model, Closed-loop, Preview, Steering control, Driver, Vehicle dynamics, Directional control, Braking control, Man-machine, Path Following, Simulation, Driver-vehicle.

Dynamic loading of road pavements

Abstract: The paper describes an experiment using a 4-axle articulated heavy goods vehicle, instrumented to measure instantaneous changes in load applied to a road by the tires of the semi-trailer The measurements of applied wheel load and strain in the pavement permitted an investigation of the effects of vehicle dynamics and pavement profile on dynamic loading and pavement performance

Analyses of moving dynamic loads on highway pavements: part i - vehicle responses

Abstract: The influence of heavy vehicle dynamics on flexible pavement response is investigated in this paper. Full non-linear models were used to describe the dynamic behavior of articulated vehicles traversing random flexible pavements in order to predict the forces at the road/tire interface. Both leaf spring and air bag suspensions are modeled. The paper provides a description of the mathematical representation of the dynamic vehicle-pavement interaction. Also discussed are the effects of varying various vehicle parameters on road damage calculated VESYS and using the modified Road Stress Factor. The parameters examined are suspension type, friction parameters, shock absorber damping, tire pressure, axle load sharing coefficients and suspension spring constants.

A laser-based highway-speed road profile measuring system

Abstract: A large proportion of road roughness measuring equipment used throughout the world today is based on transducers which sense the relative movement between the vehicle body and its rear axle. Although these systems are reliable, simple to use, and have the capacity for the measurements to be performed over a range of travel speeds, the resulting roughness statistic is influenced by the ride characteristics of the host vehicle. In most cases the data are of limited use in the detailed study of vehicle dynamics. Other problems are calibration of the roughness vehicle, comparison between similar and dissimilar systems, and stability of the measures over time. To circumvent these problems, road profile based reference systems are gaining popularity with a resulting increase in useful data for vehicle dynamicists. To meet this need, the Australian Road Research Board (ARRB) has developed a highway speed, road profile measuring system to collect profile data on Australian roads. This device and the signal processing are described in this paper and some results are presented.

On vehicle longitudinal controller design

Abstract: Two methodologies for designing a longitudinal controller for an automated vehicle are presented and compared. The first, parameter scheduling, involves a linearization of vehicle dynamics about a number of operating points, and the specification of an observer/controller compensator for each of those points. The second emphasizes an explicit accounting for nonlinearities in the selection of a nonlinear observer/controller compensator. The utility of these approaches was evaluated by designing a controller for vehicle operation on dry roads under nonemergency conditions and then evaluating controlled vehicle performance by a digital computer simulation. In contrast to the first approach, the second approach can be extended to design an observer/controller compensator for the full range of such conditions. >

Simulating a Powered Model Wheel-Tractor on Soft Ground

Abstract: THE Highway-Vehicle-Object Simulation Model S(HVOSM) and the associated computer programs prowere modified to simulate the general dynamics of a mantractor on soft ground by incorporating some soil proparameters. The simulated results were verified for passtractor overturns using a powered model tractor. The passresults showed that the modified HVOSM allowed close proprediction of vehicle dynamics.

Active Four-Wheel-Steering Design for an Advanced Vehicle

Abstract: The design of a control system to coordinate the steering of the four wheels of an advanced vehicle is described. The Linear Quadratic Gaussian, design process is applied to a directional dynamics model that includes yaw, lateral, and roll degrees-of-freedom for the vehicle and steering rotation degrees-of-freedom for the front and rear wheels. Vehicle oscillations, overshoot, sideslip, and response times to steering inputs are minimized at all forward speeds. Left-to-right steering corrections augment the control design to eliminate tire scrub and squeal in low speed and parking maneuvers. Simulation results illustrate the advantages of active four-wheel-steering over two-wheel-steering and proportional four-wheel-steering and the insensivity of the design to changes in vehicle speed, trim, loading, and tire characteristics.

Vehicle dynamics in real-time simulation

Abstract: SUMMARY This paper presents some ideas on a new concept, named COMPACT (Computer Simulation of Passenger Cars and Trucks). COMPACT was developed for the mathematical description of vehicles in all driving situations. As COMPACT is completely adopted to the particular problems in road vehicle dynamics, it results in a computer code where execution time is minimized. Thus, even real-time application at the Daimler-Benz driving simulator is possible.

Numerical analysis of roadside design (nard). volume 4. validation report. final report

Abstract: NARD is a finite element code with the capability of simulating vehicle dynamics and maneuvering, and vehicle crashes with roadside objects. The vehicle is modeled as a three-dimensional lumped parameter articulated body consisting of multiple units. The barrier is modeled as a three-dimensional object represented by displacement finite elements. Large deflections and rotations and nonlinear material behavior are accommodated in the program. The vehicle/barrier interaction is modeled by geometrically determining the interference between the two surfaces. The NARD code resulted from extensive revisions and modifications of an earlier computer code, called CRUNCH.

Cae for vehicle dynamics

Abstract: Computer–aided engineering (CAE) in vehicle dynamics consists of three subsystems, namely measurement, evaluation and prediction. It is important that each sub–system evolves in harmony with the others to ensure system co–ordination. Some remarkable attempts at using this CAE system are described here, such as the measurement of steady–state cornering, the evaluation of transient response with steering input, and prediction using full–vehicle models. The CAE approach will penetrate the motor vehicle industry at a high pace, and will contribute to the development and enhancement of suspension technology.

Directional dynamics of multi-articulated heavy trucks employing controlled steering of dolly wheels

Abstract: This chapter analyzes results that have been obtained in a study of the directional dynamics and mechanics of heavy vehicle combinations employing full trailers. In a design synthesis context, the specialized models provide the type of information used in creating (developing) new designs and explaining them. More comprehensive models (and experiments with prototype vehicles) can then be used to quantify the expected performances of the new designs. Steering usually is controlled by a mechanical linkage driven by the yaw articulation motion between the dolly and the towing trailer. The controlled steering B-dolly retains the B-dolly drawbar construction, and therefore its critical roll coupling capability. It eliminates the yaw degree of freedom at the coupling to the first trailer, and it provides for control of the steer angle of the dolly tires as a function of the included angle between the two trailers.

An adaptive control model of a car-driver and the computer simulation of the closed-loop system

Abstract: SUMMARY As the cornering stiffness of tire decreases on a wet surface, the performances of course tracking and course holding become worse. To compensate the deterioration of the vehicle dynamics, drivers tend to operate the steering wheel in a certain sense of adaptation. In this paper, a new adaptive control model of a human driver is presented using the theory of model reference adaptive control system (MRAC). The word “adaptive” in this paper means that the steering gain of a driver is not constant but changeable, corresponding to the change of vehicle parameters. With this adaptive control model, the computer simulation of the closed-loop system is carried out when the driver is going to modify his steering maneuver on wet surface.

Nonlinear and Nonstationary Random Vibration of Hysteretic Systems with Application to Vehicle Dynamics

Abstract: The nonstationary response of a nonlinear multi-degree of freedom vehicle model is obtained. The suspension is of hysteretic nonlinear type and nonstationarity is due to variable velocity traverse. The road excitation is modelled as the response of a time variant filter to modulated white noise. Equivalent linearization method is adopted and response statistics are obtained by numerical integration of matrix differential equations.

An adaptive control model of a car-driver and computer simulation of the closed-loop system --the dynamics of vehicles on roads and tracks. proceedings of the 10th iavsd symposium, prague, czech, august 24-28, 1987

Abstract: As the cornering stiffness of tyre decreases on a wet surface, the performances of course tracking and course holding become worse. In order to compensate for the deterioration of the vehicle dynamics, drivers tend to operate the steering wheel in a different manner. In this paper, a new adaptive control model of a human driver is presented, using the theory of model reference adaptive control system (mrac). The word "adaptive" in this paper means that the steering gain of a driver is not constant but changeable, corresponding to the change of vehicle parameters. With this adaptive control model the computer simulation of the closed loop system is carried out when the driver is going to modify his steering manoeuvre on a wet surface.(a) for the covering abstract of the conference see IRRD 813891.

A New Design Concept of Vehicle Dynamics Based on Active Control

Abstract: The application of an active control, such as four-wheel steering and active suspension, to cars has changed not only the vehicle dynamics design but also the dynamic characteristics of cars. Active four-wheel steering reduces the sideslip angles of the wheels, thus the unnecessary yawing motion of cars decreases and the time lag in the dynamic response to handling also decreases. An active roll control of the car body makes use of type properties to the best advantage. The four-wheel steering and active suspension upgrade the dynamic performance of cars, and expand the limit performance of dynamics. An adaptive control, integrated control and intelligent control will be introduced to cars, completely changing vehicle dynamics of cars in the near future.

Instrumental variable identification in vehicle dynamics

Abstract: SUMMARY The paper deals with the identification of physical parameters in vehicle dynamics from measurement data. The dynamical behaviour of the vehicle is modeled by a finite-dimensional, linear, time-invariant, time-continuous, mechanical system. The identification procedure has respect to several aspects such as the inclusion of hydraulic or electrical substructures to the mechanical system, the efficient use of the available sensor configuration, the necessity of external feedback to stabilize the system, and the finiteness and the noise corruption of the data set. An instrumental variable identification algorithm is constructed for the solution of a related time-discrete parameter estimation problem which leads by subsequent backtransformation and reconstruction techniques to the desired physical parameters of the original time-continuous mechanical system. The new efficient algorithm of parameter estimation is applied to a magnetically levitated vehicle. The related suspension control system is a re...

Optimal Reentry Guidance for Aeroassisted Orbit Transfer Vehicles

Abstract: A three-state model is presented for analyzing the problem of optimal changes in heading with minimum energy loss for a hypersonic gliding vehicle. A further model order reduction to a single state model is examined using singular perturbation theory. the optimal solution for the reduced problem defines an optimal altitude profile dependent on the current energy of the vehicle. A separate boundary layer analysis is used to account for altitude and flight path angle dynamics, and to obtain lift and bank angle control solutions. By considering alternative approximations to solve the boundary layer problem, three guidance laws are obtained, each having a feedback form. The guidance laws are evaluated for a hypothetical vehicle, and compared to an optimal solution obtained using a multiple shooting algorithm.

Adaptive guidance for an aero-assisted boost vehicle

Abstract: An adaptive guidance system incorporating dynamic pressure constraint is studied for a single stage to low earth orbit (LEO) aero-assist booster with thrust gimbal angle as the control variable. To derive an adaptive guidance law, cubic spline functions are used to represent the ascent profile. The booster flight to LEO is divided into initial and terminal phases. In the initial phase, the ascent profile is continuously updated to maximize the performance of the boost vehicle enroute. A linear feedback control is used in the terminal phase to guide the aero-assisted booster onto the desired LEO. The computer simulation of the vehicle dynamics considers a rotating spherical earth, inverse square (Newtonian) gravity field and an exponential model for the earth's atmospheric density. This adaptive guidance algorithm is capable of handling large deviations in both atmospheric conditions and modeling uncertainties, while ensuring maximum booster performance.

Numerical analysis of roadside design (nard). volume 1. users manual. final report

Abstract: NARD is a finite element code with the capability of simulating vehicle dynamics and maneuvering, and vehicle crashes with roadside objects. The vehicle is modeled as a three-dimensional lumped parameter articulated body consisting of multiple units. The barrier is modeled as a three-dimensional object represented by displacement finite elements. Large deflections and rotations and nonlinear material behavior are accommodated in the program. The vehicle/barrier interaction is modeled by geometrically determining the interference between the two surfaces. The NARD code resulted from extensive revisions and modifications of an earlier computer code, called CRUNCH.